7:30 p.m.: Seattle police say two people were arrested at a May Day rally downtown as protests were held in other Northwest cities.

Seattle police said the arrest was made at Westlake Park after a 26-year-old man was arrested earlier for reportedly throwing a rock.

In Olympia, police were ordering a group of protesters to disperse Monday evening, saying "the group is not friendly." Police described the group as "members of a mob" wearing masks and said they were firing rocks from sling shots at officers as well as throwing bottles and using pepper spray. Police said they had "deployed crowd control devices."

6:08 p.m.: Downtown streets remain mostly quiet, with at least one small group of protesters gathered on the sidewalk chanting and yelling at police near Central Precinct.

6:06 p.m.: Watch over two hours of the protest broadcast on Facebook Live by reporter Jim Ryan:

6 p.m.: Portland police spokesman Sgt. Pete Simpson says he doesn't yet have a number of arrested but he will provide full updates tonight.

5:53 p.m.: Other vandalism damage now being discovered, including broken windows at Brooks Brothers, Target, J. Crew, City Hall, Michael Parsons fine art, a police SUV, Goldmark Jewelers and two federal courthouses. Graffiti was sprayed on the police SUV, the Wells Fargo building, City Hall, the PacWest Center, the Nines Hotel and a Biketown bike rental kiosk, which also had bike tires slashed.

5:11 p.m.: A small fire near Southwest Sixth Avenue and Madison Street is reported, but it is extinguished quickly.

5:08 p.m.: Riot police swarm a group of protesters along the Southwest 5th Avenue transit mall near City Hall. At least eight demonstrators are taken to the ground and detained. Buses on 5th are stopped as protesters are on the ground in the street.

5:03 p.m.: Another fire is set in the street near Southwest 10th Avenue and Taylor Street.

4:59 p.m.: Police declare the protest a riot.

4:56 p.m.: Police tweet that three people have been arrested and a second fire is reported at Southwest Broadway and Morrison Street.

4:30 p.m.: Bottles are thrown at police, who announce over a loudspeaker that riot control agents may be employed and marchers may be subject to use of force. They say streets are being reopened to vehicle traffic, any marchers not on a sidewalk are subject to arrest, and that demonstrators should use sidewalks to leave the area.

4:22 p.m.: Flares are thrown at officers blocking the downtown entrance to the Morrison Bridge. No officers appear to have been hit. Police encourage all participants to leave the march.

4:18 p.m.: With marchers at Southwest 2nd Avenue and Madison Street, police on the east end of the Hawthorne Bridge temporarily block westbound motor vehicle traffic. Also, the Police Bureau on Twitter says families with children at the march should immediately leave because of violence from anarchists.

4:11 p.m.: A window has been broken at the Gus J. Solomon U.S. Courthouse. A slingshot was reportedly used. Police say that in addition to rocks and Pepsi cans, lead balls are being thrown at officers, and that anarchists are causing problems:

Anarchists committing acts of violence/property damage during #MayDayPDX march. Permitted group encouraged to separate from them.

3:54 p.m.: Police say marchers threw rocks at officers near Southwest 4th Avenue and Columbia Street. No one was injured, but it is prompting officers to put on their helmets. Also, a medic was hit but uninjured by a full Pepsi can that was thrown.

Shortly before 1 p.m., a large group of Portland State University students walked up the park blocks and arrived at Shemanski Park, which is at the northern end of the park blocks.

With half an hour before the rally was scheduled to begin, the park was mostly full. A group carrying a sign "Buddhist Peace Fellowship" quietly walked the perimeter of the park. By the beginning of the rally, almost two of the park blocks were filled.

The rally began as scheduled about 2 p.m., as speeches being given in English and Spanish, with one speaker explaining the history of May Day. Other speakers advocated unity and solidarity, and implored the crowd to stick together during the march. One asked Gov. Kate Brown and Attorney General Ellen Rosenblum to keep ICE agents out of state courts

Almost 50 various groups were represented at the gathering, with dozens of signs advocating for causes from worker, civil, student and immigration rights. A group of anarchists were near the back of the crowd, occasionally burning U.S. flags.

A youth and family zone was set up near the back of the park, which was filled with colorful balloons, banners, costumes and props.

No arrests had been made by the start of the march, but police said they have confiscated several sticks, poles and homemade shields.

The march began about 3:30 p.m. (see live updates above for up-to-the-minute details)

A rally was also being held in Salem, where hundreds gathered on the Capitol steps for a rally. Speakers included Gov. Kate Brown, Rep. Teresa Alonso Leon, D-Woodburn, and Rep. Diego Hernandez, D-Portland, who spoke to the crowd in English and Spanish, and called for upholding Oregon's sanctuary law.

Speakers said they would not be intimidated by any crackdowns on immigrants who are in the U.S. illegally. One protester carried a sign saying bridges should be built instead of walls, referring to President Donald Trump's plans to build a wall between the U.S. and Mexico.

Brown said that as long as she's in office, Oregon will be welcoming and inclusive to all those who call the state home. She said she met with farmers last week who are concerned new federal policies will devastate their businesses. The agricultural industry fears a crackdown will deprive it of the labor it needs.

And in Seattle, hundreds of people marched through downtown chanting, "Stand up, fight back," to support immigrants and workers. Native American dancers walked in front of the large gathering of protesters. The march followed a rally at a city park where speakers, including Seattle City Councilwoman Kshama Sawant, urged resistance to President Donald Trump's policies.

Seattle police say they ultimately expect up to 1,500 people to take part in the march, and a large police presence was noticeable. Later Monday anti-capitalist gatherings were expected throughout the city. The city traditionally sees large, disruptive May Day gatherings. Last year Seattle police used pepper spray to disperse black-clad protesters. Five officers were hurt, none seriously, and police arrested nine people.

Afternoon commuters in downtown Portland were advised to adjust accordingly. TriMet officials have planned unrelated service disruptions for the MAX to complete upgrades and repairs to the tracks at Southwest Morrison and Yamhill streets.

Organizers say people carrying yellow balloons will help lead the march and attempt to ensure people stay on the planned route. Organizers are also planning to have peacekeeping and de-escalation teams, but "they are not police and they will not be making arrests or working with police," according to an online information sheet. "If you need assistance, yell out 'peacekeeper'" to find one near you, the sheet says.

A separate group, the Anarchist Student Union, has announced it plans to join the rally and march. According to a Facebook page, 111 people have indicated they are going and another 337 have expressed interest.

"We'll respect the organizers and people of the permitted march to a point, then we shall do our own thing," organizers said on Facebook. "It would be ideal to actually form a bloc this May Day for our own safety. That means we stick together and we watch each other's backs."

TriMet announced its ticket office at Pioneer Courthouse Square closed at 2 p.m. because of the planned march.